1. Field of the Invention
The present invention relates to a color cathode ray tube apparatus having a color cathode ray tube and a deflecting unit mounted outside the tube.
2. Description of the Related Art
A color cathode ray tube generally comprises a panel, a funnel continuous to the panel, and a tube having a cylindrical neck connected to the funnel. A shadow mask is arranged inside the panel, and a phosphor screen constituted by three color light emission layers for emitting red, green and blue beams is formed on the inner surface of the panel to oppose the shadow mask. An electron gun assembly for emitting three electron beams is arranged inside the neck portion. I order to deflect the three electron beams emitted from the electron gun assembly in horizontal and vertical directions, a deflecting unit is arranged outside the boundary between the neck and the funnel. A static convergence magnet and a purity magnet are arranged outside the neck.
In the above color cathode ray tube apparatus, in order to display an image without color misregistration, the three electron beams must be correctly landed on the three color phosphor layers, respectively. For this reason, a deflecting unit must be mounted on a correct portion of the color cathode ray tube. In addition, the positions of the static convergence magnet and the purity magnet must be adjusted to focus the three electron beams at one central point on the phosphor screen.
In the above color cathode ray tube apparatus, an in-line electron gun assembly for emitting a pair of side beams and a center beam in a line on the same horizontal plane is generally employed. In this in-line color cathode ray tube apparatus, a phosphor screen is constituted by phosphor stripe layers extending in the vertical direction.
In the in-line color cathode ray tube apparatus, a pincushion horizontal deflecting magnetic field which is a nonuniform magnetic field is generated to deflect electron beams in the horizontal direction, and a barrel vertical deflecting magnetic field which is a nonuniform magnetic field is generated to deflect the electron beams in the vertical direction. Therefore, correction of dynamic convergence using a external circuit is not necessary. However, the mounting positions of the deflecting device, the static convergence magnet, and the purity magnet must be adjusted.
An operator conventionally adjusts the mounting positions of the deflecting unit, the static convergence magnet and the purity magnet while watching the screen. There are various types of methods of adjusting the deflecting unit, i.e., rotation of the deflecting unit on the color picture tube, reciprocation of the deflecting unit in the axial direction of the tube to correctly radiate the three electron beams on the three color phosphor layers, and swinging of the deflecting unit on the phosphor side in vertical and horizontal directions to focus the three electron beams on a peripheral portion of the phosphor screen while the deflecting unit on the electron gun assembly side is fixed. The positions of the static convergence magnet and the purity magnet are generally adjusted by rotating three pairs of magnets, i.e., a total of six annular magnets, and all of the adjusting operations are manually performed by visual check. The adjusting operations must be repeated until an optimal adjustment state is obtained. Therefore, the adjustment requires skills and time-consuming operations.
In a large color picture tube which has a high production ratio compared with other picture tubes, it is difficult for one operator to adjust the positions of a deflecting unit, a static convergence magnet, and a purity magnet each located at the rear position of the picture tube while watching an image displayed on the front image display screen. Therefore, one operator watches the screen, and the other operator cooperates to adjust the positions. Otherwise, any adjusting tool is required to adjust the positions by one operator. Therefore, the adjustment requires a time-consuming operation, and an optimal adjusting operation is difficult to obtain.
As described above, in order to display an excellent image without color misregistration on the screen of the color picture tube, the mounting positions of the deflecting unit, the static convergence magnet, and the purity magnet must be adjusted. In these adjusting operations, there are many types of operations for particularly adjusting the deflecting unit on the color picture tube. That is, these operations include items for rotating the deflecting unit on the color picture tube, moving the unit in a direction of the tube axis and swinging the unit in the vertical and horizontal directions. Since an operator manually performs these adjusting operations while watching the screen, the adjustment requires skills and a time-consuming operation. In a large tube, in particular, since the adjusting operation cannot be performed by one operator, a pair of operators cooperate to adjust the deflecting unit or any special-purpose adjusting tool is required. Therefore, the adjustment is time-consuming and cannot be optimally performed.